1. Field of the Invention
The present invention relates to a decoding circuit which operates to decode coded video data including non-reference frame data (i.e., frame data that do not refer to other frame data) and reference frame data (i.e., frame data that refer to other frame data).
2. Description of the Related Art
In Japan, the digital TV broadcasting service for mobile communications (generally referred to as “One segment broadcasting” or “One Seg”) has been available since April 2006. The apparatus, such as an automotive vehicle TV, can receive one-segment broadcasting in weak electric field areas and also receive 12-segment broadcasting (Hi-Vision broadcasting) in strong electric field areas, as discussed in Wataru KAMEYAMA et al: “MPEG-1/MPEG-2/MPEG-4 Digital Broadcasting Textbook (Vol. I)”, IDG Japan, pp. 75 to 88.
In general, the apparatus takes a relatively long time to switch from the display of the 12-segment broadcasting to the display of the one-segment broadcasting. This is because the interval between decode reference pictures (IDR pictures) for the one-segment broadcasting is long compared to that for the 12-segment broadcasting. Therefore, there is a significant waiting time before the next decode start reference picture is received.
As a method for quickly starting a display of data, it may be useful to decode both one-segment data and 12-segment data concurrently and switch a picture to be displayed depending on the situation. However, this method is disadvantageous in electric power consumption and the bandwidth of Synchronous Dynamic Random Access Memory (SDRAM), compared to a switching-type decoder.